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Velocity Measurement Spikes on NI-9760 When Using Hall Mode

Updated Apr 10, 2018

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Hardware

NI-9760

Issue Details

When I am acquiring velocity measurements from my NI-9760 in Hall Mode (i.e. when zero crossing and internal threshold are configured to be false), I observe sporadic large spikes in my velocity measurement on one or more of my channels, as shown below:

Figure 1. Velocity Measurement Spikes on NI-9760

Solution

This behavior is due to the susceptibility of the NI-9760 in Hall mode to noise, which results in occasional spikes in velocity when the NI-9760 counts a false pulse that has occurred due to noise in the system.

To resolve this issue, NI recommends using a debounce filter in the FPGA for any applications with the NI-9760 that require the use of Hall Mode.